Another thing to consider is what you want to do with the MPH in the end - it is an amazingly diverse degree but you don't want to go into the program just for the sake of a few extra letters behind your name. I defend my MPH thesis next Thursday from the Univ of MN program - I entered that before med school and finished my coursework about 3.5 yrs ago, began my thesis #1, had to trash it and start over, and have only been able to give minimal time and attention to it once starting med school (i just finished year 2 at DMU-OMC).
It's great to learn about preventative med (I think preventative med residencies require it, or else incorporate it into the residency) and very general things that are NOT taught in med school, but it's also a very different focus. Medicine is focused on the individual, and public health could care less about the individual and focuses on trends and groups - it doesn't matter if one person has a heart attack.
In my cohort (about 15 people in my entering class) there were about 5 of us that knew we wanted to eventually end up in medicine, and took electives accordingly. There are quite a few in policy, working with the dept of public health, or working for agencies or on research studies.
It's a great program, and very fun, but it does take some time and effort, and it's a very different focus than what most people coming from biological sciences/hard sciences/medicine are used to. There are some programs you can do via correspondance, but so much of the discipline (at least as it was taught to me) is involved with working with groups, that you'd have to look very critically at distance programs (I really have never looked at any, so please dont' flame me).
Good luck.
MPH on Thursday finally!!!!!